I have just completed my compression test on my MGB. It is 162(1) 161(2) 160 (3) 162 (4) . Are these results ok? I have a problem with my 3rd spark plug. It is always black, no oil just carbon, number 1, 2, and 4 are fine. I wonder was could be the problem, valves, or sticky ring? Could anybody please let me know if the compression test results are good , and how to solve the problem with the dirty number 3 cylinder plug.

Thanks, everyone, the plugs are the spec Champion plugs. I will check the plug gap. The carbs were recently tuned with a vacuum gauge to sync the intake and idle. The mixture was set to spec appears to be running a bit rich, I can lean it out a bit to see if this helps.

73 MGB. Tires: Round, black, hold air. Oil: Sometimes old, sometimes new...always slippery. Oil filter: Yellow, usually full of oil. Carbs: 2 SU HIF. Distributor: Yes. Headlights: Not that bright but bright enough. A bunch of other stuff most cars have but not really important enough to itemize. Oh, wait...it has a cool sounding exhaust with stickers on the chrome tips. Really slays the ladies...

That plug, plug-wire, cap or rotor might not be firing consistently on that cylinder. Try swapping plugs to see if the probably follows the plug, if not do the same thing with the plug-wire, if the probably is still on #3, replace the rotor and cap. Also inspect the dizzy shaft to ensure it is not bent.